Motorized machine electrical system arc detection apparatus and methods

ABSTRACT

Disclosed is a motorized machine which includes an electrical system monitoring system which results in detecting arcing in the electrical distribution system of the machine and the ability to provide notification and protection for such arcing. The system functions to monitor the electrical distribution system of the machine to sense the frequencies of signals in the system using appropriate filtering. One type of filtering which may be used is based upon a heterodyning circuit which provides variable frequency filtering for filtering a signal representative of the current in at least one electrical circuit of the machine. The heterodyning circuit output is configured to produce a signal which may be logarithmically related to the filtered signal. If the output signal exceeds a predetermined limit (representative of noise) for a predetermined period (representative of a typical arc duration), the system generates an arc signal. The arc signal may then be used to operate a circuit interrupter or an indicator in a circuit protection system or both.

FIELD OF THE INVENTION

The present invention relates, in general, to arc fault detection and,more specifically, to arc fault detection in an electrical distributionsystem of a motorized machine.

BACKGROUND OF THE INVENTION

There are various conditions that may cause an arc fault. Corroded, wornor aged wiring or insulation, insufficient contact pressure, electricalstress from repeated overloading, etc., may result in an arc fault.These conditions may damage the insulation of the wiring and createexcessive heating temperatures. In general, these conditions have beenfound to occur in applications where vibrations and relatively hightemperatures are normally present. More specifically, vehicles (e.g.automobiles, airplanes, trucks, off-road equipment, etc.) and othermoving or vibrating equipment provide a harsh environment forelectronics and electrical systems (direct current (D.C.) or alternatingcurrent (A.C.)).

The development of electronics and electrically powered accessories hasresulted in an increase in the use of electronics and electrical powerin vehicles. Examples of electronics and electrically poweredaccessories used in vehicles include:

electronic fuel injection or fuel control;

electronic timing control;

electronic transmission shift control;

electronic HVAC control;

electronic lighting control;

electronic braking control (e.g. anti-lock braking, traction control,slip control, etc.);

power convenience accessories (e.g. power seats, power windows, heatedseats, personal lighting, heated steering wheels, power sun roof, powersteering wheel tilt, power mirrors, tire inflation control, etc.);

electronic cruise control;

on-aboard navigation systems; and

air bags.

Many of the electronics and power accessories listed above are also usedin aircraft and off-road vehicles (e.g. tractors, tracked vehicles,excavators, etc.). With hybrid and pure electric vehicles, the use andtransmission of electrical power is multiples greater than withconventional vehicles due to the use of electricity to power the motorswhich propel the vehicles.

As a result of the substantial increase in use of electronics andelectrical power accessories in vehicles, and the use of electric motorsto propel vehicles, the potential for arc faults in the electricalsystems of vehicles has also increased. As discussed above, such arcingcan damage wiring and electronics or, cause unwanted heating. Thus, itwould be desirable to provide a system for detecting and controlling arcfaults in vehicle electrical systems.

Detection and control of arc faults is relatively complicated. Forexample, the occurrence of an arc fault in one branch circuit of a powerdistribution system of a vehicle may generate a false arc detectionsignal in another branch circuit. As a result, circuit breakers orinterrupters in more than one branch circuit may erroneously trip.Relatively noisy loads within the vehicle, such as electric motors(engine fan, heater fan, power seat motors, etc.) can create highfrequency disturbances, which may appear to be arc faults and causeunwanted circuit breaker tripping. Similarly, external high frequencydisturbances within the machines' operative environment also may appearto be arc faults and cause unwanted circuit tripping.

There are two types of arc faults that may occur in a vehicle. A firsttype is a high-energy arc that may be related to high current faults; asecond type is a low current arc that may be related to the formation ofa carbonized path between conductors. The first type may result from aninadvertent connection between a line conductor and neutral conductor ora line conductor and ground. The first type may draw current that isabove the rated capacity of the circuit, arcing as the conductors arephysically joined.

The other type of arc fault, the carbonization between electricalconductors, may be considered more problematic. Since the current in thearc may be limited to less than the trip rating of an associated circuitbreaker or interrupter, such arcs may become persistent withoutobservation and may result in certain conditions. Contact arcs may becaused by springs in switches that become worn which, in turn, mayreduce the forces that hold electrical contacts together. As theelectrical contacts heat and cool down, the conductors may touch andseparate repeatedly, thereby possibly creating arcs known as “sputteringarcs.” Such sputtering arcs can create carbonized paths resulting inpersistent low current arcs in the electrical system.

Contact arcs or sputtering arcs may also be observed in contacts whichare made from different materials. For example, aluminum wiring whichcontacts copper wiring may oxidize at the contact points. In this case anon-conductive layer may build up over time between the contact pointsand arcing may result.

In view of the potential for arc faults in vehicles, it would bedesirable to provide vehicles with arc fault detection.

SUMMARY OF THE INVENTION

The present invention provides a motorized machine which generatesvibration during operation. The machine includes a motor configured togenerate mechanical energy, a source of electrical energy, at least oneelectrical load having a function, an electrical distribution systemconfigured to couple the electrical load to the source of electricalenergy, and a circuit protection system coupled to the electricaldistribution system. The circuit protection system is configured tointerrupt application of electrical energy from the source of electricalenergy or to indicate an arc event in response to an arc signal. Anelectrical arc detection circuit is coupled to the circuit protectionsystem and is configured to monitor the electrical energy and generatethe arc signal when the electrical energy generates a signalrepresentative of an electrical arc.

Another embodiment of the invention provides a method for detecting anarcing fault in a motorized machine that generates vibration, with themotorized machine having an electrical distribution system including acircuit protection system, a source of electric energy, and at least oneelectrical load having a function. The method of arc detection comprisesthe steps of monitoring the electrical distribution system with asuperheterodyne circuit, generating an oscillator frequency which cyclesbetween a low frequency and a high frequency. The oscillator circuit iscoupled to the superheterodyne circuit. Eliminating background andspurious noise with a comparator circuit coupled to the superheterodynecircuit in a reference voltage terminal. Monitoring time of the arcingfault based on a signal from the comparator circuit with an arc timingmonitor circuit. Compensating for arcing drop-outs based on signal fromthe arc timing monitor circuit with a compensating circuit. Generating afurther signal indicative of the arc fault if the predetermined timeperiod if exceeded with an accumulating circuit based on the signal fromthe compensating circuit and, generating an arc signal to operate thecircuit protection system, with the trip signal generation circuit basedon further signal from the accumulating circuit. Another embodiment ofthe method of arc detection includes the step of activating one of acircuit interrupter and an indicator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram representation of a vehicle including anembodiment of an arc detection circuit.

FIG. 2 is a detailed circuit diagram of an exemplary embodiment of anarc detection circuit.

FIG. 3 is a detailed circuit diagram of a simulated arc generationcircuit.

FIG. 4 is a detailed circuit diagram of an exemplary embodiment of a DCarc detection circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram representation of a vehicle or a machine 10whether land, air or sea based. Vehicle 10 includes a D.C. energystorage power source 12 (e.g., a battery), an A.C. or D.C. power source14 (e.g. a generator or alternator driven by engine 16, a fuel cell, ora photovoltaic device such as a solar cell array), a motor engine 16,engine controls 18, heating, ventilating and air conditioning system 20(HVAC), lighting 22, traction and braking system controls 24, a brakingsystem 26, an application function control A 28, and an applicationspecific function control B 30. If the vehicle is a land based vehiclesuch as an automobile, truck or off-road machine equipment (e.g.tractor, excavator, tracked vehicle or construction equipment), thevehicle could also include electronic transmission controls 32, atransmission 34, and typically at least one driven wheel 36 and mayinclude an implement 37. The implement 37 can be, for example, a spindlecoupled to the motor 16 for spinning a material against a tool forshaping the material, or a movable arm coupled to the motor 16 to movematerials in a predetermined manner such as a crane or a backhoe.

In general, in land based vehicle 10, motor engine 16 is mechanicallycoupled to transmission 34 which is mechanically coupled to at least onedrive wheel 36. In operation the mechanical energy from engine 16 istransmitted through transmission 34 which controls the direction andspeed of wheel 36 relative to engine speed 16. In most modern vehiclessuch as automobiles, engine 16 is controlled by electronic enginecontrols 18. Such controls 18 typically control electronic fuelinjection, electronic timing and, in some cases, electronic enginevalves. In most modern vehicles such as automobiles, high poweredtractors and off-road equipment, electronic transmission controls 32control the shifting of transmission 34 based upon parameters such asengine speed signals from electronic engine control 18, and signals fromthe electronic braking and traction control systems 24.

The HVAC system 20 typically includes temperature controls and airmovement fans. Lighting system 22 typically includes the vehiclelighting and the appropriate lighting controls which vary substantiallyfrom vehicle to vehicle. More specifically, in addition to the primaryvehicle lighting provided to permit vehicle operation in the dark, manyvehicles include interior lighting systems for instruments andcompartment lighting.

Referring to traction and braking system controls 24, these controls arecoupled to the braking system 26 and, as discussed briefly above, totransmission control 32. Traction control systems are generally knownand operate to pulse the brakes on various wheels of a vehicle toredirect power flow through the vehicle differentials to limit theapplication of power to a wheel spinning at a rate high relative to theother powered wheel(s) of the vehicle. The braking system control inmost modern vehicles is commonly referred to as an antilock brakingsystem and operates to relieve pressure on the brakes when the systemdetermines that the wheel associated with a particular brake is slidingrelative to the surface upon which the vehicle is traveling.

FIG. 1 includes two application function controls 28 and 30. However,depending upon on the vehicle or machine, this number may vary. Oneexample of an application specific function control would be theelectronics and control system for an onboard navigation system 38.Another example of an application specific function control would be thecontrol for the vehicle air bags 40. Other examples of systems which mayrequire applications specific function controls include power seats,power windows, heated seats, personal lighting, heated steering wheels,power sun roofs, power steering wheel tilt, power mirrors, tireinflation control, off-road vehicle slip control, electronic cruisecontrol, etc.

In vehicles and machines, including substantial numbers of theelectronic controls and electrically powered accessories such as thosediscussed above, all of these controls require power from a power sourcesuch as D.C. power source 12 which in most vehicles and machines is astorage battery which in turn today is charged by A.C. power source 14,that is typically an alternator and appropriate voltage regulator andrectification system. Alternatively, a D.C. generator can be used tocharge the battery. As vehicle electronics and wiring systems becomemore complicated, a range of circuit protection 42 is provided. Manycircuits in vehicles are currently protected by passive circuitprotection such as fuses which are responsive to a very limited type ofcircuit fault. These limited types of circuit fault are short circuitand overload.

One of the problems with having a limited range of circuit protection isthe absence of protection for circuits when arcing is occurring withinthe electrical system. Such arcing can create noise within the systemwhich can interfere with sensitive electronics and, more dangerously,can create fire within the vehicle. Accordingly, circuit protection 42includes a circuit interrupter 48, such as for example, controllablemechanical or semiconductor circuit interrupters and fuses forinterrupting the application of D.C. power to the vehicle electronics.In particular, power source 12 is coupled to engine controls 18,transmission control 32, HVAC system 20, lighting 22, traction controland braking system controls 24, application specific function control A28 and application specific function control B 30 with circuitprotection system 42. In operation, circuit protection system 42 caninterrupt power supplied to the various electronics via electricaldistribution system 41 power conductors 18A, 32A, 20A, 22A, 24A, 28A and30A.

In some applications, the circuit protection system 42 includes anindicator 49 that enunciates an arcing event in the one or more specificfunctions in the vehicle electronic system. Specific functions, such aselectronic braking or window motors, should not have power cut-off,notwithstanding arcing. In such instances when the arc detection circuit44 detects an arcing event, an arc signal is sent to the circuitprotection system 42 which in turn activates the indicator 49. Theindicator 49 can be a visual display that may comprise a warning light,an audible signal, including a message, tone or noise or a tactileindicator such as a vibrating surface in contact with the systemoperator. The indicator 49 can be located within the vicinity of theoperator of the vehicle 10 or machine having the arc detection circuit44 to alert the operator to the arcing event with the operator thentaking appropriate action. Thus, at the option of the arc detectionsystem designer, the circuit protection system 42 can be configured toenunciate an arcing event, interrupt electrical power-supply or both.

To protect against arcing within the vehicle electronic system an arcdetection circuit 44 is provided. In particular, an arc detectioncircuit 44 is configured to detect signals generated within one or moreconductors 18A, 32A, 20A, 22A, 24A, 28A or 30A which are representativeof arcing within the electrical circuits, electronics and electricalequipment associated with these circuits. In simpler systems, arcdetection circuit 44 may only monitor the power conductor from source12. Of course, the specific monitoring scheme can be varied dependingupon cost constraints, detection accuracy requirements, reliabilityrequirements, etc.

In operation, arc detection circuit 44 monitors the conductors todetermine if arcing is present. If an arcing event is present, circuit44 provides an arc signal to the circuit protection system 42 alongsignal conductor 46 to activate an indicator 49 to notify the systemoperator, or the circuit interrupter 48, which then will trip one ormore of the circuit breakers or circuit interrupters associated with theconductors to provide power from power source 12 to the respectivecontrols and electrical equipment or both. Signal conductor 46 mayinclude one or more signal conductors depending upon a number ofconductors being monitored for arcing.

Depending upon the vehicle and electronics being provided power, circuitprotection system 42 may include indicators 49 and circuit interrupters48 such as electronically controlled circuit breakers or appropriatesemiconductor switches which can be controlled (opened or closed) basedupon a signal from arc detection circuit 44.

Vehicle 10 was described above as a land based vehicle. However, vehicle10 could be any other type of vehicle including an airplane, jet, boat,etc. Depending upon the type of vehicle, the engine may be a pistonengine or turbine engine and may be fueled by gasoline, diesel fuel,natural gas, etc. In the case of an airplane or jet, vehicle 10 wouldnot include a transmission 34 or transmission controls 32. Rather,propulsion of the vehicle would be generated directly from turbine(s) orpropeller(s) coupled to the engine(s) 16.

The use of vehicle electronics and electrically powered components hasincreased and continues to increase in vehicles. These increases invehicle electronics has resulted in substantial rises in currents inconventional automotive powered systems which have typically a range of12-14 volts. As a result, it is likely that battery voltages will beincreased to voltages above 12 volts (e.g. range of 36 volts to 42 voltsnominal). Currently, most over-the-road semi-trucks include 24 voltsystems and aircraft include AC voltage systems for example nominal 24volts AC. These increased voltages will also increase the potential forarcing due to the fact that increased voltages permit arcing to occurover larger air gaps.

Notwithstanding the range of voltages mentioned, the detectiontechniques described herein are not voltage sensitive. The technique forAC circuits applies for all AC voltages and likewise, the technique forDC circuits applies to all DC voltages.

Referring now to FIG. 2, FIG. 2 is a detailed circuit diagram of arcdetection circuit 44. In general, arc detection circuit 44 includes anoscillator 50, a heterodyning chip 52 such as chip number SA626manufactured by Phillips Semiconductor, a power source 54, a levelcomparator circuit 56, and arc time monitoring circuit 58, one shotcircuit 60, a time accumulating circuit 62, and a trip signal generationcircuit 64. Oscillator 50 is coupled to the oscillator inputs OSE-E andOSC-B of heterodyning chip 52. In general, oscillator 50 is configuredto generate an oscillator frequency which cycles between a low frequencyand a high frequency. Ideally, this frequency range would be as broad aspossible if it were not cost and component restrained. Some applicationsmay permit costs which would support a range of 20.0 to 40.0 megahertz,and the circuitry shown in FIG. 2 provides an oscillator which generatesoscillator frequencies which cycle from 30.0 to 35.0 megahertz whereinthe oscillator cycles from the low to the high oscillator frequency inless than one millisecond.

Power supply 54 is a D.C. power supply which supplies three (3) volts tocircuit 52 as shown in FIG. 2. This power supply is connected to theD.C. power source 12, but could be configured for connection to A.C.power source 14.

Circuit 52 monitors an electrical circuit (i.e. voltage or current) atthe RF_(in) and RF_(out) pins. Depending upon the application these pinsare coupled to the positive and/or negative conductors in the circuit.The particular configuration shown in FIG. 2 is for connection to anA.C. system with the conductors of the system being connected at RF_(in)and RF_(out) of chip 52. Chip 52 is also coupled as shown to two 10.7megahertz filters 80 and 82. These filters were selected based upon thefrequencies which are permitted for RF circuit use by the U.S.Government. However, depending upon future availability or uses for thecircuit, these filters may be changed to filter at other centerfrequencies. Chip 52 is wired as shown in FIG. 2 so that chip 52operates to subtract the frequency of the signal input at RF_(in) andRF_(out) from the frequency of oscillator 50, and filter the differencein these frequencies at 10.7 megahertz. The result is that circuit 52provides a variable frequency filter.

An analysis of arcing in both A.C. and D.C. circuits shows that arcinggenerates relatively high amplitude signals across a very large range offrequencies including at least 20.0 through 40.0 megahertz. Accordingly,since oscillator 50 oscillates between 30.0 and 35.0 megahertz, chip 52will generate a continuously high signal at the RSSI output throughoutthe oscillation of oscillator 50 when arcing is occurring in the systemcoupled to the RF input 51 of chip 52. However, when chip 52 merelydetects signals which exist at selected frequencies between 30.0 and35.0 megahertz, chip 52 will only generate spikes or pulses at the RSSIoutputs.

Circuit 52 provides logarithymic amplification to the filtereddifference between the oscillator 50 signal and the signal applied toRF_(in) and RF_(out). By way of example, this signal generated at RSSIis set to be within a range of 0 to 1 volts wherein that voltage is anindication of the decibel level of the input signal RF_(in).

The signal at RSSI is applied to comparator circuit 56. Circuit 56includes a comparator 66 and reference voltage terminals 68. Inoperation, comparator circuit 56 changes output state (e.g. goes high)only if a voltage generated by circuit 52 exceeds the predeterminedvoltage reference set at terminal 68. The purpose of comparator circuit56 is to eliminate the effects of background and spurious noise on arcdetection. If the signal generated at the RSSI output is greater thanthe reference signal 68 the output of comparator 66 is set high (i.e.changes state from the normal state representative of no arcing to astate representative of arcing). The signal at the output of comparator66 is applied to time monitoring circuit 58.

Time monitoring circuit 58 operates to determine if the time the outputof comparator 66 is high is indicative of the time period (e.g.milliseconds or more) of a typical arcing event. If the time period issufficient, then time monitoring circuit 58 applies a signal to one shotcircuit 60 which compensates for the extinguishing of an arc when thevoltage of the monitored A.C. power goes through the zero crossing. Thepurpose of the mono-stable multi-vibrator circuit (60) also generallyknown as a one-shot circuit, is to count the number of arcinghalf-cycles in an AC wave form.

The signal from one shot circuit 60 is applied to accumulating circuit62 which determines if there has been arcing for at least apredetermined number of half cycles (e.g. three) of the A.C. systembeing monitored for arcing. If arcing exists for a predetermined numberof half cycles, a signal is applied by circuit 62 to trip circuit 64which outputs a trip signal on conductor 46 to operate a circuitinterrupter such as a circuit breaker or provide a signal to operate anindicator 49.

The components of the vehicle described in reference to FIG. 1 wouldnormally require D.C. electrical power. The detection circuit of FIG. 2is configured for an A.C. system and is readily converted into arcdetection circuit for a D.C. electrical system. In particular, toconvert the circuit of FIG. 2 to an arc detection circuit for a D.C.electrical system, a 1.0 k resistor 141 is inserted at the output ofcomparator 66, and capacitor 150 and diode 156 of one-shot circuit 60are removed and replaced by a direct connection between the output ofcomparator 146 and the negative input of comparator 164. The threeassociated resistors 152, 154, and 158 of one shot circuit 60 areremoved as well as resistor 148. It should be understood that “removed”as used herein may mean simply disconnecting the appropriate lead in thecircuit. An exemplary embodiment of a DC circuit is illustrated in FIG.4. The purpose of this change is to compensate the lack of zerocrossings in D.C. circuits. Arcing drop outs compensated for typicallyhave variable durations, for example 0.5 millisecond or 1.0 millisecond.

To monitor the desired electrical circuit either current transformers(CT) or shunts can be used as appropriate to couple the RF inputs ofchip 52 to the circuit to be monitored. Depending upon the applicationand type of loads on electrical circuits either a CT or shunt and therespective configuration thereof would be chosen. For example, for A.C.and D.C. applications it is desirable to eliminate fundamental A.C. orD.C. current signals. Since the frequency range of interest for thecircuit shown in FIG. 2 is between 30.0 and 35.0 megahertz, the core ofa CT would be a low permeability core. Such low permeability coreprovides relatively good immunity from noise signals in the kilohertzrange.

Referring to FIG. 3, FIG. 3 illustrates a test circuit 70 including acontact switch having contacts 72 and an output terminal 74 which iscoupled to ground wherein the conductor 76 from transistor 78 passesthrough the system CT. In operation, when contacts 72 are brought intocontact, circuit 70 generates a signal which simulates arcing throughconductor 76 which is then monitored by the current transformerassociated with the A.C. arc detection circuit of FIG. 2 or the D.C. arcdetection circuit of FIG. 4 discussed above.

The following is a table listing all of the components set out in FIGS.2, 3 and 4 and their associated reference numbers, component types andvalues or part references as applicable.

Component Value or Reference No. Component Type Part Reference 52Heterodyning SA626 Circuit 66 Comparator LM2901 78 Transistor 2N3904 8010.7 MH_(z) Filter SFECA10.7MAS 82 10.7 MH_(z) Filter SFECA10.7MAS 84Capacitor 0.1 μF 86 Resistor 5.49 k ohms 88 Resistor 3.74 k ohms 90Comparator LM 2904 92 Resistor 66.5 k ohms 94 Resistor 22.1 k ohms 96Resistor 33.2 k ohms 98 Capacitor 0.074 μF 100 Operational LM2904Amplifier 102 Resistor 51 k ohms 104 Diode MV 7005 106 Capacitor 68 pF108 Capacitor 39 pF 110 Inductor 33 nH 112 Capacitor 39 pF 114 Resistor22.1 k ohms 116 Capacitor 39 pF 118 Capacitor 1000 pF 120 Capacitor 1000pF 122 Capacitor 1000 pF 124 Capacitor 1000 pF 126 Capacitor 1000 pF 128Capacitor 0.1 μF 130 Resistor 4.99 k ohms 132 Resistor 4.02 k ohms 136Resistor 2.3 k ohms 138 Resistor 86.6 k ohms 140 Capacitor 0.033 μF 141Resistor 1.0 k ohms 142 Resistor 11.3 k ohms 144 Resistor 33.2 k ohms146 Operational LM2901 Amplifier 148 Resistor 20 k ohms 150 Capacitor.01 μF 152 Resistor 60 k ohms 154 Resistor 60 k ohms 156 Diode 1N4148158 Resistor 60 k ohms 160 Resistor 5 k ohms 162 Resistor 20 k ohms 164Operational LM2901 Amplifier 166 Resistor 20 k ohms 168 Transistor2N3904 170 Resistor 42 k ohms 172 Resistor 9 k ohms 174 Capacitor 0.1 μF176 Resistor 150k ohms 178 Resistor 150k ohms 180 Resistor 20 k ohms 182Transistor 2N3904 184 Resistor 10 k ohms 186 Operational LM2901Amplifier 188 Resistor 20 k ohms 190 Capacitor 0.01 μF 192 Resistor 10 kohms 194 Transistor 2N3904 196 Resistor 8 k ohms 198 Resistor 10 k ohms200 Capacitor 0.01 μF 202 SCR EC103D 204 Capacitor 0.1 μF 206 VoltageRegulator LM317 208 Resistor 20 k ohms 210 Resistor 150 k ohms 212Resistor 48 k ohms 214 Resistor 10 k ohms 216 Transistor 2N3904 218Resistor 1 k ohms 219 Capacitor 0.1 μF 220 Capacitor 0.01 μF 222Transistor 2N3904 224 Transistor 2N3904 226 Resistor 68 k ohms 228Resistor 510 k ohms 230 Capacitor 1.2 nF 232 Transistor 2N3904

While two embodiments and multiple applications for the arc detectionsystem have been disclosed and described in detail, various othermodifications could be considered within the scope of the invention. Forexample, it is contemplated that the A.C. or D.C. arc detection would beusable in vibrating equipment such as machine tools, robots, and othermanufacturing equipment. By way of another example, the center filterfrequency of 10.7 megahertz may be modified depending upon frequenciesmade available by the Government in the future and the particularapplication for the arc detection. Furthermore, depending upon componentavailability and cost the frequency range and cycling frequency ofoscillator circuit 50 may be modified to suit particular applications,cost constraints and component availability. Still furthermore, it iscontemplated that all or a portion of the circuitry disclosed may beembodied on a single chip, and further modifications may includemultiple channels of arc detection. These modifications and otherapplications are intended to be covered in the scope of the appendedclaims.

What is claimed is:
 1. A motorized machine which generates vibrationduring operation, the machine comprising: a motor configured to generatemechanical energy; a source of electrical energy; at least oneelectrical load having a function, wherein the load requires electricalenergy to accomplish the function; an electrical distribution systemconfigured to couple the electrical load to the source of electricalenergy; a superheterodyne circuit configured to monitor the electricaldistribution system; a circuit protection system coupled to theelectrical distribution system; and, an electrical arc detection circuitcoupled to the circuit protection system and configured to monitor theelectrical energy and generate an arc signal when the electrical energygenerates a signal representative of an electrical arc, furthercomprising an electrical conductor of the electrical distribution systemwhich couples to the electrical load to the source of electrical energy,and the detection circuit includes a current transformer coupled to theelectrical conductor.
 2. The machine of claim 1, wherein the electricaldetection system includes: an oscillator circuit configured to generatean oscillator frequency which cycles between a low frequency and a highfrequency, with the oscillator circuit coupled to the superheterodynecircuit; a comparator circuit configured to eliminate background endspurious noise, the comparator circuit coupled to the superheterodynecircuit and a reference voltage terminal; an arc timing monitor circuitconfigured to monitor time of the arcing fault based on signal from thecomparator circuit; a compensating circuit configured to compensate forarcing drop outs when signal from the arc timing monitor circuit isreceived by the compensating circuit; an accumulating circuit configuredto receive the signal from the compensating circuit and generate afurther signal indicative of the arc fault if a predetermined timeperiod is exceeded; and, a trip signal generation circuit configured toreceive the further signal from the accumulating circuit and generate anarc signal to operate the circuit protection system.
 3. The machine ofclaim 2, wherein the circuit protection system includes one of a circuitinterrupter and an indicator.
 4. The machine of claim 3, wherein thecircuit protection system is configured to interrupt application ofelectrical energy from at least one of the electrical storage device andthe electrical power source in response to the arc signal.
 5. Themachine of claim 3, wherein the circuit protection system is configuredto signal an arcing event with one of a group including, a display, alight, an audible message, an audible tone, an audible noise and atactile indicator.
 6. The machine of claim 1, wherein the electricalload requires electrical energy provided at a relatively constantvoltage.
 7. The machine of claim 3, further comprising a spindle coupledto the motor for spinning a material against a tool for shaping thematerial.
 8. The machine of claim 3, further comprising a movable armcoupled to the motor to move materials in a predetermined manner.
 9. Themachine of claim 3, further comprising at least one wheel coupled to themotor to move the machine.
 10. A method for detecting an arcing fault ina motorized machine that generates vibration, with the motorized machinehave an electrical distribution system including a circuit protectionsystem, a source of electrical energy, and at least one electrical loadhaving a function, the method of arc detection comprising the steps of:monitoring the electrical distribution system with a superheterodynecircuit; generating an oscillator frequency which cycles between a lowfrequency and a high frequency, with an oscillator circuit coupled tothe superheterodyne circuit; eliminating background and spurious noisewith a comparator circuit coupled to the superheterodyne circuit and areference voltage terminal; monitoring time of the arcing fault based ona signal from the comparator circuit with an arc timing monitor circuit;compensating for arcing drop outs based on signal from the arc timingmonitor circuit with a compensating circuit; generating a further signalindicative of the arc fault if a predetermined time period is exceeded,with an accumulating circuit based on the signal from the compensatingcircuit; and, generating an arc signal to operate the circuit protectionsystem, with a trip signal generation circuit based on the furthersignal from the accumulating circuit.
 11. The method of arc detection ofclaim 10, including the step of coupling a first filter to thesuperheterodyne circuit.
 12. The method of arc detection of claim 11,including the step of coupling a second filter to the superheterodynecircuit.
 13. The method of arc detection of claim 12, wherein eachfilter is configured to operate at a frequency of 10.7 megahertz. 14.The method of arc detection of claim 13, including the step ofinstalling the arc detection circuit in a vehicle.
 15. The method of arcdetection of claim 10, including the step of activating one of a circuitinterrupter and an indicator.
 16. The method of arc detection of claim15, wherein the circuit protection system is configured to interruptapplication of electrical energy from at least one of the electricalstorage device and the electrical power source in response to the arcsignal.
 17. The method of arc detection of claim 15, wherein the circuitprotection system is configured to signal an arcing event with one of agroup including, a display, a light, an audible message, an audibletone, an audible noise and a tactile indicator.
 18. The method of arcdetection of claim 10, including the step of coupling an implement tothe motorized machine.
 19. The method of arc detection of claim 18,wherein the implement is selected from a group including: a spindle, amovable arm and a wheel.